1. Field of the Invention
The invention is related to the field of telecommunications, and in particular, to an area based sub-path protection for communication networks.
2. Description of the Prior Art
Communication networks include network elements that are connected to each other through communication links. Some examples of network elements are transceivers, switches, routers, and cross-connect devices. Some of these network elements use optical technology to exchange communications over optical fiber links. One such technology is wavelength division multiplexing (WDM), where each wavelength of an optical signal carries a different channel of communications. Thus, an optical fiber link carries a number of channels of communications using WDM.
These optical transmission channels between two network elements are called lightpaths. A lightpath may travel through multiple fiber links. Some lightpaths operate at the rate of a few gigabits per second (Gbps). In some communication networks without wavelength converters, a lightpath occupies the same wavelength on all the fiber links it traverses, which is referred to as wavelength continuity. When using lightpaths, the routing of the lightpaths and the wavelength assignment of lightpaths are determined.
In one example of the communication networks, the network elements within the communication network are connected in a ring configuration. Each network element is connected to two other network elements to form a ring. Some rings are connected to other rings, where shared network elements are stacked to interconnect rings. These ring configurations have poor scalability and use excessive resource redundancy for failure recovery. Thus, network configurations are migrating from ring network to mesh networks, where network elements are connected to two or more network elements. In another example, a communication network using Internet Protocol (IP) is partitioned into regional areas for control and management purposes.
Network element or optical fiber link failure in a communication network results in loss of data or delays in data, which both result in revenue loss. There are two types of fault management to handle the failure of the network element or optical fiber link: protection and restoration. Restoration is a reactive procedure in which spare capacity is available after the fault's occurrence is utilized for rerouting the disrupted connections. Protection is a proactive procedure in which spare capacity is reserved as a backup resource during connection setup. A working path of a connection is setup, which is the path carrying the connection under normal operations. When a failure occurs on the working path of a connection, a portion of or the entire connection is switched to the pre-reserved backup resource.
Protection schemes are classified by type of rerouting and type of resource sharing. In a link-based rerouting, the connections are rerouted around the end network elements of the failed link. In a path-based rerouting, a backup path is selected between the end nodes of the working path. In a dedicated resource protection, the network resources such as wavelengths are not shared among backup paths. In a shared resource protection, the backup paths do share resources such as wavelengths, which utilizes network resources more efficiently. In shared-path protection, the backup paths can share resources as long as the corresponding primary paths are not in the same shared risk group (SRG). Two primary paths are in the same SRG if they traverse the same fiber, or the fibers they traverse are in the same cable or in the same duct.
Some prior solutions for mesh WDM communication networks use protection schemes that protect the communication network as a whole. Some of these prior solutions use integer linear programs (ILP) or simulated annealing based heuristics to solve routing and planning of capacity. These ILPs and heuristics minimize the total cost of a given static traffic demand set. However, as the communication networks increase in size, there are problems with long protection switching time and poor scalability.
Other prior solutions decompose a mesh communication network into different structures such as rings, protection cycles, p-cycles, and trees. Some of these prior solutions then perform automatic protection switching based on these individual structures. However, these prior solutions suffer from excessive resource redundancy.